Semiconductor devices and methods of forming the same

ABSTRACT

According to embodiments of the inventive concept, a gate electrode is formed on a substrate, and a first spacer, a second spacer, and a third spacer are sequentially formed on a sidewall of the gate electrode. The substrate is etched to form a recess region. A compressive stress pattern is formed in the recess region. A protective spacer is formed on a sidewall of the third spacer. When the recess region is formed, a lower portion of the second spacer is removed to form a gap region between the first and third spacers. The protective spacer fills the gap region.

CROSS-REFERENCE TO RELATED APPLICATIONS

This U.S. non-provisional patent application claims priority under 35U.S.C. §119 to Korean Patent Application No. 10-2012-0105406, filed onSep. 21, 2012, the entirety of which is incorporated by referenceherein.

BACKGROUND

The inventive concept relates to semiconductor devices and methods offorming semiconductor devices.

Semiconductor devices are widely used in the electronics industrybecause of their small size, multi-functionality, and/or low manufacturecosts. Accordingly, the development of semiconductor devices has beenhighly integrated with the development of the electronic industry.Widths and the spacing of patterns in semiconductor devices have beenfurther and further reduced for higher integration of semiconductordevices. For recently targeted high levels of integration ofsemiconductor devices, however, new exposure techniques and/or veryexpensive exposure techniques are required, increasing the difficulty ofachieving higher degrees of integration of the semiconductor devices.Thus, various research has been conducted for new integratingtechniques.

SUMMARY

Embodiments of the inventive concept may provide semiconductor deviceswith improved reliability and methods of forming semiconductor deviceswith improved reliability.

Embodiments of the inventive concept may also include semiconductordevices capable of decreasing or preventing non-uniformity of thresholdvoltages of transistors and methods of forming the same.

In one aspect, a method of forming a semiconductor device may include:forming a gate electrode on a substrate; sequentially forming a firstspacer, then a second spacer, and then a third spacer on a sidewall ofthe gate electrode; etching the substrate to form a recess region;forming a compressive stress pattern in the recess region; and forming aprotective spacer on a sidewall of the third spacer. A lower portion ofthe second spacer may be removed during the formation of the recessregion such that a gap region may be formed between the first spacer andthe third spacer. The protective spacer may fill the gap region.

In some embodiments, the first spacer may be formed of the same materialas the third spacer; and the protective spacer may be formed of amaterial having an etch selectivity with respect to the first and thirdspacers.

In some embodiments, the recess region may expose a bottom surface ofthe second spacer.

In some embodiments, forming the recess region may include removing anatural oxide layer formed in an inner surface of the recess regionduring etching the substrate. In this case, the lower portion of thesecond spacer may be removed together with the natural oxide layer.

In some embodiments, the method may further include performing a thermaltreating process and/or a plasma treating process on the semiconductordevice after forming the protective spacer.

In some embodiments, the method may further include forming a deviceisolation layer defining an active region of the substrate. A portion ofthe device isolation layer may be removed during the formation of therecess region such that a bottom surface of the second spacer may beexposed.

In some embodiments, the gate electrode may be formed on the deviceisolation layer.

In some embodiments, the protective spacer may be formed after thecompressive stress pattern is formed.

In some embodiments, the method may further include forming a cappingpattern on the gate electrode before forming the first spacer andremoving the capping pattern after forming the compressive stresspattern. The capping pattern may be formed of the same material as thefirst and third spacers; and the third spacer may be prevented frombeing etched by the protective spacer when the capping pattern isremoved.

In another aspect, a semiconductor device may include: a gate dielectriclayer and a gate electrode provided on a top surface of a substrate,where the gate dielectric is positioned between the substrate and thegate electrode; an inner spacer and an outer spacer provided on asidewall of the gate electrode, where the inner spacer is positionedbetween the gate-electrode sidewall and the outer spacer; and acompressive stress pattern provided in the substrate adjacent to thegate electrode. A top surface of the compressive stress pattern may becloser to a bottom surface of the substrate than is a bottom surface ofthe gate dielectric layer. A top surface of the inner spacer may be at aheight from the substrate that is greater than half of the height thatthe gate electrode extends from the substrate and be closer to thesubstrate than is a top surface of the gate electrode. The outer spacermay extend between the inner spacer and the compressive stress pattern.

In some embodiments, the gate electrode may include a lower gateelectrode on the gate dielectric layer and an upper gate electrode onthe lower gate electrode; and the lower gate electrode may include ametal and/or a conductive metal nitride.

In some embodiments, the inner spacer may include: a first spacer, asecond spacer, and a third spacer sequentially formed on the sidewall ofthe gate electrode, with first spacer positioned between the sidewall ofthe gate dielectric and the second spacer, and with the second spacerpositioned between the first spacer and the third spacer; and aprotecting pattern filling a gap region defined by a bottom surface ofthe second spacer and the sidewalls of the first and third spacers.

In some embodiments, the gap region may extend at least partiallybetween the lower gate electrode and the substrate (i.e., in theorientations shown in the figures, the gap region may horizontallyoverlap with the lower gate electrode—likewise, other directional ororientational indications made here are in reference to the orientationshown in the figures).

In some embodiments, the second spacer and the protecting pattern mayinclude a material having an etch selectivity with respect to the firstand third spacers.

In some embodiments, the gate electrode may be provided on a deviceisolation layer defining an active region of the substrate; and theinner spacer may overlap with the compressive stress pattern along anaxis normal to the bottom surface of the substrate (i.e., in theorientations shown in the figures, the inner spacer may verticallyoverlap with the compressive stress pattern).

In another aspect, a method of forming a semiconductor device includesthe following: forming a gate electrode comprising at least one of ametal, a conductive metal nitride, and doped semiconductor material on asubstrate comprising silicon, wherein the gate electrode includes atleast one sidewall; sequentially forming a first spacer, then a secondspacer, and then a third spacer on the sidewall of the gate electrode,wherein the first and third spacers comprise silicon nitride, whereinthe second spacer comprises a silicon oxide and includes a lowerportion, and wherein each spacer includes at least one sidewall; etchingthe substrate to form a recess region, wherein the lower portion of thesecond spacer is removed during the formation of the recess region suchthat a gap region is formed between the first spacer and the thirdspacer; performing a selective epitaxial growth process in the recess toform a compressive stress pattern in the recess region; and forming aprotective spacer on the sidewall of the third spacer and filling thegap region with the protective spacer, wherein the protective spacercomprises at least one of a silicon oxide and silicon nitride.

In some embodiments, the compressive stress pattern may be doped withp-type dopant.

In some embodiments, the compressive stress patterns may comprisecrystalline silicon-germanium.

In some embodiments, the etching of the substrate to form the recessregion may include the following steps: selectively etching portions ofthe substrate to form preliminary recess regions on opposite sides ofthe gate electrode, wherein inner surfaces of the preliminary recessregions react with oxygen to form a first natural oxide layer; removingthe first natural oxide layer via etching; then further etching thepreliminary recess regions to form the recess regions, wherein innersurfaces of the recess regions react with oxygen to form a secondnatural oxide layer; removing the second natural oxide layer viaetching, wherein a lower portion of the second spacer proximate thesubstrate is removed when the second natural oxide layer is removed.

In some embodiments, a top surface of the gate electrode, remote fromthe substrate, may be covered with a lower capping pattern comprising asilicon oxide; and the lower capping pattern may be covered with anupper capping pattern comprising silicon nitride.

BRIEF DESCRIPTION OF THE DRAWINGS

The inventive concept will become more apparent in view of the attacheddrawings and accompanying detailed description.

FIGS. 1A, 1B, 2A, 2B, 3A, 3B, 4A, 4B, 5A, 6, 7A, 7B, 8A, 8B, 9A, 9B,10A, 10B, 11A and 11B are cross-sectional views illustrating asemiconductor device and a method of forming the same according to someembodiments of the inventive concept;

FIG. 5B is an enlarged view of a portion ‘D’ of FIG. 5A;

FIG. 9C is an enlarged view of a portion ‘F’ of FIG. 9A;

FIGS. 12A and 12B are cross-sectional views a semiconductor device and amethod of forming the same according to other embodiments of theinventive concept; and

FIG. 13 is a schematic block diagram illustrating an example ofelectronic systems including semiconductor devices according toembodiments of the inventive concept.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The inventive concept will now be described more fully hereinafter withreference to the accompanying drawings, in which exemplary embodimentsof the inventive concept are shown. The advantages and features of theinventive concept and methods of achieving them will be apparent fromthe following exemplary embodiments that will be described in moredetail with reference to the accompanying drawings. It should be noted,however, that the inventive concept is not limited to the followingexemplary embodiments, and may be implemented in various forms.Accordingly, the exemplary embodiments are provided only to disclose theinventive concept and to let those skilled in the art know the categoryof the inventive concept. In the drawings, embodiments of the inventiveconcept are not limited to the specific examples provided herein, andfeatures in the illustrations may be exaggerated for clarity.

The terminology used herein is for the purpose of describing particularembodiments and is not intended to limit the invention. As used herein,the singular terms “a,” “an” and “the” are intended to include theplural forms as well, unless the context clearly indicates otherwise. Asused herein, the term “and/or” includes any and all combinations of oneor more of the associated listed items. It will be understood that whenan element is referred to as being “connected” or “coupled” to anotherelement, it may be directly connected or coupled to the other element orintervening elements may be present.

Similarly, it will be understood that when an element, such as a layer,region or substrate, is referred to as being “on” another element, itcan be directly on the other element or intervening elements may bepresent. In contrast, the term “directly” means that there are nointervening elements. It will be further understood that the terms“comprises”, “comprising”, “includes” and/or “including”, when usedherein, specify the presence of stated features, integers, steps,operations, elements, and/or components, but do not preclude thepresence or addition of one or more other features, integers, steps,operations, elements, components, and/or groups thereof.

It will also be understood that although the terms first, second, third,etc., may be used herein to describe various elements, these elementsshould not be limited by these terms. These terms are only used todistinguish one element from another element. Thus, a first element insome embodiments could be termed a second element in other embodimentswithout departing from the teachings of the present invention. Exemplaryembodiments of aspects of the present inventive concept explained andillustrated herein include their complementary counterparts. The samereference numerals or the same reference designators denote the sameelements throughout the specification.

Moreover, exemplary embodiments are described herein with reference tocross-sectional illustrations and/or plane illustrations that areidealized exemplary illustrations. Accordingly, variations from theshapes of the illustrations as a result, for example, of manufacturingtechniques and/or tolerances, are to be expected. Thus, exemplaryembodiments should not be construed as being limited to the shapes ofregions illustrated herein but are to include deviations in shapes thatresult, for example, from manufacturing. For example, an etching regionillustrated as a rectangle will, typically, have rounded or curvedfeatures. Thus, the regions illustrated in the figures are schematic innature and their shapes do not necessarily illustrate the actual shapeof a region of a device and are not intended to limit the scope ofexample embodiments.

FIGS. 1A to 11A and 1B to 11B are cross-sectional views illustrating asemiconductor device and a method of forming the same according to someembodiments of the inventive concept. FIGS. 1A to 11A arecross-sectional views of a first region 10 and a second region 20 of asubstrate. FIGS. 1B to 11B are cross-sectional views of a third region30 of the substrate. FIG. 5C is an enlarged view of a portion ‘D’ ofFIG. 5A, and FIG. 9C is an enlarged view of a portion ‘F’ of FIG. 9A.

Referring to FIGS. 1A and 1B, a substrate 100 including the first,second, and third regions 10, 20, and 30 may be provided. The substrate100 may include a semiconductor-based structure. For example, thesubstrate 100 may be a silicon substrate or a silicon-on-insulator (SOI)substrate. In some embodiments, the first region 10 and the secondregion 20 may be p-channel metal-on-semiconductor (PMOS) regions of asemiconductor device in which PMOS transistors are respectively formed.The third region 30 may be an n-channel metal-on-semiconductor (NMOS)region of the semiconductor device in which an NMOS transistor isformed. The substrate 100 of the first and second regions 10 and 20 maybe doped with n-type dopants, and the substrate 100 of the third region30 may be doped with p-type dopants.

A gate dielectric layer, a gate electrode layer, a lower capping layer,and an upper capping layer may be sequentially formed on the substrate100 and then may be patterned to form gate structures on the first,second, and third regions 10, 20, and 30, respectively. The gatestructure on the first region 10 may include a first gate dielectricpattern 111, a first gate electrode pattern G1, a first lower cappingpattern 131, and a first upper capping pattern 135, which aresequentially stacked. The gate structure on the second region 20 mayinclude a second gate dielectric pattern 112, a second gate electrodepattern G2, a second lower capping pattern 132, and a second uppercapping pattern 136, which are sequentially stacked. The gate structureon the third region 30 may include a third gate dielectric pattern 113,a third gate electrode pattern G3, a third lower capping pattern 133,and a third upper capping pattern 137, which are sequentially stacked.

The first to third gate electrodes G1, G2, and G3 may be formed on thesubstrate 100 of the first to third regions 10, 20, and 30,respectively. The first gate electrode pattern G1 may be formed on anactive region defined in the first region 10, and the third gateelectrode pattern G3 may be formed on an active region defined in thethird region 30. The active region of the first region 10 and the activeregion of the third region 30 may correspond to a portion of thesubstrate 100 of the first region 10 and a portion of the substrate 100of the third region 30, respectively. The second gate electrode patternG2 may be formed on a device isolation layer 110 formed in the substrate100 of the second region 20 and may define an active region in thesecond region 20. In other words, the first gate dielectric pattern 111may be disposed between the first gate electrode pattern G1 and thesubstrate 100, and the third gate dielectric pattern 113 may be disposedbetween the third gate electrode pattern G3 and the substrate 100. Thesecond gate dielectric pattern 112 may be disposed between the secondgate electrode pattern G2 and the device isolation layer 110. Forexample, the device isolation layer 110 may include a silicon oxide(e.g., SiO₂) and/or a silicon oxynitride layer. The first to third lowercapping patterns 131, 132, and 133 may be formed on the first to thirdgate electrodes patterns G1, G2, and G3, respectively. The first tothird upper capping patterns 135, 136, and 137 may be formed on thefirst to third lower capping patterns 131, 132, and 133, respectively.

The first to third gate dielectric patterns 111, 112, and 113 mayinclude a high-k dielectric material having a dielectric constantgreater than that of silicon oxide. For example, the first to third gatedielectric patterns 111, 112, and 113 may include at least one ofhafnium oxide (HfO₂), aluminum oxide (Al₂O₃), or tantalum oxide (Ta₂O₅).In other embodiments, the first to third gate dielectric patterns 111,112, and 113 may include at least one of silicon oxide, siliconoxynitride, or silicon nitride. In some embodiments, the first to thirdgate dielectric patterns 111, 112, and 113 may be formed by at least oneof a chemical vapor deposition (CVD) process, an atomic layer deposition(ALD) process, or a thermal oxidation process.

The first to third gate electrode patterns G1, G2, and G3 may includelower gate electrodes 121, 122, and 123 and upper gate electrodes 125,126, and 127 on the lower gate electrodes 121, 122, and 123. In someembodiments, the upper gate electrodes 125, 126, and 127 may be thickerthan the lower gate electrodes 121, 122, and 123. The lower gateelectrodes 121, 122, and 123 may include a metal and/or a conductivemetal nitride. For example, the lower gate electrodes 121, 122, and 123may include titanium nitride (TiN), tantalum nitride (TaN), or tungstennitride (W_(x)N_(y)). In some embodiments, the upper gate electrodes125, 126, and 127 may include a doped semiconductor material, such asdoped silicon, doped silicon-germanium, or doped germanium. For example,the upper gate electrodes 125, 126, and 127 may include dopedpoly-silicon or doped amorphous silicon. The first to third gateelectrode patterns G1, G2, and G3 may be formed using at least one of aCVD process, an ALD process, or a sputtering process.

The upper capping patterns 135, 136, and 137 may be formed of a materialhaving an etch selectivity with respect to the lower capping patterns131, 132, and 133 (i.e., the upper capping patterns are etched at ahigher rate than the lower capping patters). For example, the lowercapping patterns 131, 132, and 133 may include a silicon oxide, and theupper capping patterns 135, 136, and 137 may include silicon nitride.The upper capping patterns 135, 136, and 137 may be thicker than thelower capping patterns 131, 132, and 133; and the lower capping patterns131, 132, and 133 and the upper capping patterns 135, 136, and 137 maybe formed using CVD processes.

First spacers 202, 203, and 204 may be formed on sidewalls of the firstto third gate electrode patterns G1, G2, and G3, respectively. A firstinsulating layer may be formed to cover the substrate 100; and then thefirst insulating layer may be anisotropically etched to form the firstspacers 202, 203, and 204. The first insulating layer may be etched byan anisotropic dry etching process. Second spacers 212, 213, and 214 maybe formed on sidewalls of the first spacers 202, 203, and 204,respectively. A second insulating layer may be formed to cover the firstspacers 202, 203, and 204; and then the second insulating layer may beanisotropically etched by an anisotropic dry etching process to form thesecond spacers 212, 213, and 214. The first spacers 202, 203, and 204may be formed of a material having an etch selectivity with respect tothe second spacers 212, 213, and 214. In some embodiments, the firstspacers 202, 203, and 204 may be formed of the same material as theupper capping patterns 135, 136, and 137; and the second spacers 212,213, and 214 may be formed of the same material as the lower cappingpatterns 131, 132, 133. For example, the first spacers 202, 203, and 204may include silicon nitride, and the second spacers 212, 213, and 214may include a silicon oxide.

Referring to FIGS. 2A and 2B, third spacers 222 and 223 may be formed onsidewalls of the second spacers 212 and 213 of the first and secondregions 10 and 20, respectively; and a masking insulating layer 224 maybe formed on the substrate 100 of the third region 30. A thirdinsulating layer may be formed on the substrate 100 having the secondspacers 212, 213, and 214; and then a mask layer (not illustrated) maybe formed to cover the third insulating layer of the third region 30. Atthis time, the third insulating layer of the first and second regions 10and 20 may be exposed. The third insulating layer may be anisotropicallyetched using the mask layer (not illustrated) as an etch mask to formthe third spacers 222 and 223 and the masking insulating layer 224. Themasking insulating layer 224 may correspond to the third insulatinglayer of the third region 30 covered by the mask layer (notillustrated). Subsequently, the mask layer (not illustrated) may beremoved. In some embodiments, the third spacers 222 and 223 and themasking insulating layer 224 may be formed of an insulating materialhaving an etch selectivity with respect to the second spacers 212, 213,and 214. For example, the third spacers 222 and 223 and the maskinginsulating layer 224 may be formed of the same material as the firstspacers 202, 203, and 204.

Referring to FIGS. 3A and 3B, a mask pattern 50 may be formed on thesubstrate 100. The mask pattern 50 may include openings 51 respectivelyexposing portions of the substrate 100 in the first and second regions10 and 20. The openings 51 may be formed at both sides of each of thefirst and second gate electrode patterns G1 and G2, respectively. Theopenings 51 may not be provided in the mask pattern 50 of the thirdregion 30. For example, the mask pattern 50 may include at least one ofsilicon nitride or silicon oxynitride.

The substrate 100 exposed by the openings 51 may be etched using themask pattern 50 as an etch mask to form first and second preliminaryrecess regions PS1 and PS2 in an upper portion of the substrate 100. Insome embodiments, the etching process for the formation of thepreliminary recess regions PS1 and PS2 may include a dry etchingprocess. Distances d1 and d3 between the first preliminary recessregions PS1 and the first and second gate electrode patterns G1 and G2may be less than distances d2 and d4 between the second preliminaryrecess regions PS2 and the first and second gate electrode patterns G1and G2. In some embodiments, horizontal distances between the secondpreliminary recess regions PS2 and the first and second gate electrodepatterns G1 and G2 may be equal to or less than about 30 nm. Deferencebetween the distances may be caused by misalignment of the openings 51.Alternatively, a first distance d1 may be substantially equal to asecond distance d2, and a third distance d3 may be substantially equalto a fourth distance d4. In this case, gap region, described below, maybe formed at both sides of each of the first and second gate electrodepatterns G1 and G2, respectively. For the purpose of ease andconvenience in explanation, an example is described hereinafter wherethe second distance d2 is greater than the first distance d1 and wherethe fourth distance d4 is greater than the third distance d3. However,the inventive concept is not limited thereto.

During the etching process, inner surfaces of the exposed preliminaryrecess regions PS1 and PS2 may react with oxygen to form a first naturaloxide layer 61.

Referring to FIGS. 3A and 4A, the first natural oxide layer 61 may beremoved. In some embodiments, the first natural oxide layer 61 may beremoved using an etching material that includes NF₃ and/or NH₃. Afterthe mask pattern 50 is removed (see FIGS. 3B and 4B), the preliminaryrecess regions PS1 and PS2 may be further etched to form recess regionsRS1 and RS2. In some embodiments, the recess regions RS1 and RS2 may beformed by a wet etching process. In this case, an exposed top surface ofthe substrate 100 may also be etched. The substrate 100 of the thirdregion 30 may be protected from the etching process for the formation ofthe recess regions RS1 and RS2 by the masking insulating layer 224.

The etching process for the formation of the recess regions RS1 and RS2may be an anisotropic wet etching process. The anisotropic wet etchingprocess may use crystal planes of the substrate 100 as etch stop planes.In some embodiments, the anisotropic wet etching process may use {111}crystal planes of the substrate 100 as the etch stop planes. Thus, therecess regions RS1 and RS2 may be tapered toward regions under the firstand second gate electrode patterns G1 and G2 in a cross-sectional view.

If the substrate 100 is the silicon substrate, the anisotropic wetetching process may use an anisotropic etching solution includingammonia and/or tetramethyl ammonium hydroxide (TMAH).

Alternatively, the recess regions RS1 and RS2 may be formed by ananisotropic dry etching process using an etching gas having a straightetching property in a specific direction. For example, the anisotropicdry etching process may use an etching gas having the straight etchingproperty in a direction making an acute angle with a perpendiculardirection to the top surface of the substrate 100. In this case, theupper capping patterns 135 and 136 and the spacers 202, 203, 212, 213,222, and 223 and the device isolation layer 110 may be used as etchmasks.

First and second recess regions RS1 and RS2 in the second region 20 mayexpose sidewalls of the device isolation layer 110, respectively. Whenthe first and second recess regions RS1 and RS2 are formed, a portion SPof the substrate 100 existing on the sidewall of the device isolationlayer 110 may be separated from the substrate 100 to be removed. Exposedinner surfaces of the recess regions RS1 and RS2 may react with oxygento form a second natural oxide layer 62 during the etching process forthe formation of the recess regions RS1 and RS2.

Referring to FIGS. 4A, 5A, and 5B, the second natural oxide layer 62 maybe removed. For example, the second natural oxide layer 62 may beremoved by an etching material including NF₃ and/or NH₃. Upper portionsof the second spacers 212 and 213 may be etched when the second naturaloxide layer 62 is removed. The third region 30 may be protected by themasking insulating layer 224 during the removal of the second naturaloxide layer 62.

Lower portions of the second spacers 212 and 213 may be removed when thesecond natural oxide layer 62 is removed. Thus, a gap region GA may beformed between each of the first spacers 202 and 203 and each of thethird spacers 222 and 223. The gap regions GA may be defined bysidewalls of the first spacers 202 and 203, sidewalls of the thirdspacers 222 and 223 and etched bottom surfaces of the second spacers 212and 213. In some embodiments, the gap regions GA may be formed under thesecond spacers 212 and 213 adjacent to the first recess regions RS1, butmay not be formed under the second spacers 212 and 213 adjacent to thesecond recess regions RS2.

The gap region GA may be formed if the first recess region RS1 isrelatively closer to the first gate electrode pattern G1 as illustratedin the first region 10 of FIG. 5A. Compressive stress patterns,described below, may be provided in the recess regions RS1 and RS2. Asthe compressive stress patterns are more tapered toward the region underthe first gate electrode G1, mobility of carriers in a channel mayincrease. As a result, the recess regions RS1 and RS2 may expose thesecond spacers 212; and then the lower portions of the second spacers212 may be removed during the removal of the second natural oxide layer62.

The gap regions GA may be formed if the first recess region RS1 isrelatively closer to the second gate electrode pattern G2 on the deviceisolation layer 110 as illustrated in the second region 20 of FIG. 5A.If the device isolation layer 110 includes a silicon oxide, a portion DPof the device isolation layer 110 may also be removed during the removalof the second natural oxide layer 62. Thus, the lower portion of thesecond spacer 213 may be exposed and then etched.

Referring to FIG. 6, the compressive stress patterns 151 may be formedin the recess regions RS1 and RS2. The compressive stress patterns 151may be formed by a selective epitaxial growth (SEG) process performed inthe recess regions RS1 and RS2. The masking insulating layer 224 maycover the substrate 100 of the third region 30 so that the compressivestress patterns 151 may not be formed in the third region 30. If thesubstrate 100 is formed of silicon, the compressive stress patterns 151may include silicon-germanium. The compressive stress patterns 151 mayhave a crystalline state. In some embodiments, the compressive stresspatterns 151 may have a substantially single-crystal state.

The compressive stress patterns 151 may be doped with p-type dopants byan in-situ method. Alternatively, the compressive stress patterns 151may be doped with p-type dopants by an ion implantation method in asubsequent process. The compressive stress patterns 151 may increase themobility of carriers in a channel region of the semiconductor device.

Referring to FIGS. 7A and 7B, a protecting insulating layer 231 may beformed on the substrate 100 including the compressive stress patterns151. The protecting insulating layer 231 may fill the gap regions GA. Insome embodiments, the protecting insulating layer 231 may include asilicon oxide layer or a silicon nitride layer. In another embodiment,the protecting insulating layer 231 may be a multi-layer including asilicon oxide layer and a silicon nitride layer.

Referring to FIGS. 7B, 8A and 8B, an anisotropic dry etching process maybe performed on the protecting insulating layer 231 to form protectivespacers 232, 233, and 234. Portions 238 and 239 (hereinafter, referredto as “residual portions”) of the protecting insulating layer 231 mayremain on the second spacers 212 and 213, respectively. The protectivespacer 232 adjacent to the gap region GA in the first region 10 may bein contact with top surface of the compressive stress pattern 151 andmay extend into the gap region GA. A bottom surface of the protectivespacer 233 adjacent to the gap region GA in the second region 20 may bespaced apart from the compressive stress pattern 151 and the deviceisolation layer 110 and may extend into the gap region GA. Theprotecting spacers 234 in the third region 30 may be formed on themasking insulating layer 224. The inventive concept is not limited tothe aforementioned shapes of the protective spacers 232, 233, and 234;the shapes of the protective spacers 232, 233, and 234 may be variouslymodified according to a recipe of the etching process and/or shapes oflayers adjacent thereto.

After the protective spacers 232, 233, and 234 are formed, a thermaltreating process and/or a plasma treating process may be performed. Forexample, the thermal treating process may be performed at a temperatureof about 500 degrees Celsius or more.

Referring to FIGS. 8A, 8B, 8C, 9A, 9B, and 9C, the upper cappingpatterns 135, 136, and 137 may be selectively removed—for example, byapplication of phosphoric acid (H₃PO₄). The second spacers 212, 213, and214, the lower capping patterns 131, 132, and 133, and the protectivespacers 232 and 233 may not be etched due to their etch selectivity withrespect to the upper capping patterns 135, 136, and 137. On the otherhand, upper portions of the first spacers 202, 203, and 204 and thethird spacers 222 and 223 may be etched during the removal of the uppercapping patterns 135, 136, and 137. The masking insulating layer 224 inthe third region 30 may be removed along with the upper capping patterns135, 136, and 137. Thus, the protective spacers 234 on the maskinginsulating layer 224 in the third region 30 may also be removed.

The protective spacers 232 and 233 may prevent the first spacers 202 and203 from being removed in the etching process that removes the uppercapping patterns 135, 136, and 137. In other words, the protectivespacers 232 and 233 may prevent the first spacers 202 and 203 exposed bythe gap regions GA from being partially or fully removed. If theprotective spacers 232 and 233 are not present, the first spacers 202and 203 may be damaged, thereby exposing sidewalls of the lower gateelectrodes 121 and 122; and then the exposed lower gate electrodes 121and 122 may be partially or fully removed or damaged by a subsequentetching process. Thus, reliability of a semiconductor device may bedeteriorated; and non-uniformity of threshold voltages of transistorsmay be caused. However, according to some embodiments of the inventiveconcept, the first spacers 202 and 203 may be protected by theprotective spacers 232 and 233. As a result, reliability of thesemiconductor device may be improved, and non-uniformity of thethreshold voltages of the transistors may be prevented or reduced.

Referring to FIGS. 9A, 9B, 10A and 10B, the lower capping patterns 131,132, and 133 may be removed. When the lower capping patterns 131, 132,and 133 are removed, the protective spacers 232 and 233 of the first andsecond regions 10 and 20 may be partially etched to form protectingpatterns 235 and 236. Upper portions of the second spacers 212 and 213and the residual portions 238 and 239 in the first and second regions 10and 20 may also be removed during the removal of the lower cappingpatterns 131, 132, and 133. On the other hand, the second spacers 214 ofthe third region 30 differ from the second spacers 212 and 213 of thefirst and second regions 10 and 20 in that they are not covered by thethird spacers 222 and 223. Thus, the second spacers 214 of the thirdregions 30 may be completely removed when the lower capping patterns131, 132, and 133 are removed. In some embodiments, the process ofremoving the lower capping patterns 131, 132, and 133 may be performedusing an etching material including diluted HF (DHF) acid.

Referring to FIGS. 11A and 11B, outer spacers 251, 252, and 253 may beformed on sidewalls of the first, second, and third gate electrodepatterns G1, G2, and G3, respectively. The spacers and the protectingpatterns 235 and 236 between the outer spacers 251, 252, and 253 and thesidewalls of the first to third gate electrode patterns G1, G2, and G3may be defined as inner spacers 292, 293, and 294. For example, theouter spacers 251, 252, and 253 may be formed of at least one of asilicon oxide, silicon nitride, or silicon oxynitride. An interlayerinsulating layer 161 may be formed to cover the substrate 100. Theinterlayer insulating layer 161 may be formed of at least one of asilicon oxide, silicon nitride, or silicon oxynitride. The outer spacers251, 252, and 253 and the interlayer insulating layer 161 may be formedusing CVD processes.

Before the interlayer insulating layer 161 is formed, source/drainregions 191 may be formed in the substrate 100 of the third region 30.The source/drain regions 191 may be formed by an ion implantationprocess using the outer spacers 253 and the third gate electrode patternG3 as an ion implantation mask. The source/drain region 191 may be dopedregions having a conductivity type different from the conductivity typeof the substrate 100 in the third region 30. In some embodiments, thesource/drain regions 191 may be doped with N-type dopants. When thesource/drain regions 191 are formed, the substrate 100 of the first andsecond regions 10 and 20 may be covered by a mask layer (notillustrated). Thus, the ion implantation process for the formation ofthe source/drain regions 191 may not be performed in the substrate 100of the first and second regions 10 and 20.

According to some embodiments of the inventive concept, the innerspacers 292, 293, and 294 and the outer spacers 251, 252, and 253 may besequentially provided on the sidewalls of the first to third gateelectrode patterns G1, G2, and G3, respectively. The second gateelectrode pattern G2 of the second region 20 may be provided on thedevice isolation layer 110.

In the first and second regions 10 and 20, the compressive stresspatterns 151 are provided in the substrate 100 adjacent to the first andsecond gate electrode patterns G1 and G2. Top surfaces of thecompressive stress patterns 151 may be lower than bottom surfaces of thefirst and second gate dielectric patterns 111 and 112 in the illustratedorientations. A top surface of each of the inner spacers 292 and 293(particularly, a top surface of each of the first spacers 202 and 203)may be higher than half of the height of each of the first and secondgate electrode patterns G1 and G2 and may be lower than a top surface ofeach of the first and second gate electrode patterns G1 and G2. Asdescribed, herein, the “top” surfaces of these components are those thatare most remote from the substrate on which they are mounted, while the“bottom” surfaces of these components are those that are most proximateto the substrate. In the first and second regions 10 and 20, the outerspacers 251 and 252 may extend between the inner spacers 292 and 293 andthe compressive stress patterns 151.

The inner spacers 292 and 293 may include the first spacers 202 and 203,the second spacers 212 and 213, and the third spacers 222 and 223sequentially formed on the sidewalls of the first and second gateelectrode patterns G1 and G2, respectively. Additionally, the innerspacers 292 and 293 may further include the protecting patterns 235 and236 filling the gap regions GA defined by sidewalls of the first spacers202 and 203, the sidewalls of the third spacers 222 and 223, and bottomsurfaces of the second spacers 212 and 213, respectively. The secondspacers 212 and 213 and the protecting patterns 235 and 236 may includea material having an etch selectivity with respect to the first spacers202 and 203 and the third spacers 222 and 223. The inner spacers 292 and293 may be vertically overlapped with the compressive stress patterns151.

FIGS. 12A and 12B are cross-sectional views of a semiconductor deviceand a method of forming a semiconductor device according to otherembodiments of the inventive concept. For the purpose of ease andconvenience in explanation, the descriptions to the same elements as inthe aforementioned embodiment will be omitted or mentioned briefly.

According to the embodiments illustrated in FIGS. 12A and 12B, innerspacers 292, 293, and 294 may includes the first spacers 202, 203, and204. The inner spacers 292, 293, and 294, however, may not include thesecond spacers 212 and 213, the third spacers 222 and 223, and theprotecting patterns 235 and 236. In the present embodiment, the thirdspacers 222 and 223 may be removed during the removal of the uppercapping patterns 135, 136, and 137 described with reference to FIGS. 9A,9B, and 9C; and the second spacers 212 and 213 and the protectingpatterns 235 and 236 may be removed during the removal of the lowercapping patterns 131, 132, and 133, described with reference to FIGS.10A and 10B.

Other elements and other formation processes in the present embodimentmay be the same as or similar to the elements and formation processescorresponding thereto in the aforementioned embodiments of FIGS. 1A to11A and 1B to 11B.

FIG. 13 is a schematic block diagram illustrating an example ofelectronic systems including semiconductor devices according toembodiments of the inventive concept.

Referring to FIG. 13, an electronic system 1100 according to anembodiment of the inventive concept may include a controller 1110, aninput/output (I/O) unit 1120, a memory device 1130, an interface unit1140 and a data bus 1150. At least two of the controller 1110, the I/Ounit 1120, the memory device 1130 and the interface unit 1140 maycommunicate with each other through the data bus 1150. The data bus 1150may correspond to a path through which electrical signals aretransmitted.

The controller 1110 may include at least one of a microprocessor, adigital signal processor, a microcontroller or other logic devices. Theother logic devices may have a function similar to that of any one ofthe microprocessor, the digital signal processor and themicrocontroller. The I/O unit 1120 may include a keypad, a keyboardand/or a display unit. The memory device 1130 may store data and/orcommands. The memory device 1130 may include at least one of thesemiconductor devices according to the embodiments described above. Thememory device 1130 may further include another type of semiconductordevice which is different from the semiconductor devices describedabove. The interface unit 1140 may transmit electrical data to acommunication network or may receive electrical data from acommunication network. The interface unit 1140 may operate wirelessly orby cable. For example, the interface unit 1140 may include an antennafor wireless communication or a transceiver for cable communication.Although not shown in the drawings, the electronic system 1100 mayfurther include a fast DRAM device and/or a fast SRAM device that actsas a cache memory for improving an operation of the controller 1110.

The electronic system 1100 may be applied to a personal digitalassistant (PDA), a portable computer, a web tablet, a wireless phone, amobile phone, a digital music player, a memory card or any of a varietyof other electronic products. The other electronic products may receiveor transmit information data by wireless communication.

According to embodiments of the inventive concept, the reliability ofthe semiconductor device may be improved. Additionally, non-uniformityof the threshold voltages of the transistors may be reduced orprevented.

While the inventive concept has been described with reference to exampleembodiments, it will be apparent to those skilled in the art thatvarious changes and modifications may be made without departing from thespirit and scope of the inventive concept. Therefore, it should beunderstood that the above embodiments are not limiting, butillustrative. Thus, the scope of the inventive concept is to bedetermined by the broadest permissible interpretation of the followingclaims and their equivalents, and shall not be restricted or limited bythe foregoing description.

1. A method of forming a semiconductor device comprising: forming a gateelectrode on a substrate, wherein the gate electrode includes at leastone sidewall; sequentially forming a first spacer, then a second spacer,and then a third spacer on the sidewall of the gate electrode, whereinthe second spacer includes a lower portion, and wherein the third spacerincludes at least one sidewall; etching the substrate to form a recessregion; forming a compressive stress pattern in the recess region; andforming a protective spacer on the sidewall of the third spacer, whereinthe lower portion of the second spacer is removed during the formationof the recess region such that a gap region is formed between the firstspacer and the third spacer; and wherein the protective spacer fills thegap region.
 2. The method of claim 1, wherein the first spacer is formedof the same material as the third spacer; and wherein the protectivespacer is formed of a material having an etch selectivity with respectto the first and third spacers.
 3. The method of claim 1, wherein therecess region exposes a bottom surface of the second spacer during theformation of the recess region.
 4. The method of claim 1, whereinforming the recess region comprises: removing a natural oxide layerformed in an inner surface of the recess region during etching of thesubstrate; and wherein the lower portion of the second spacer is removedtogether with the natural oxide layer.
 5. The method of claim 1, furthercomprising: performing a thermal treating process and/or a plasmatreating process on the semiconductor device after forming theprotective spacer.
 6. The method of claim 1, further comprising: forminga device isolation layer defining an active region of the substrate,wherein a portion of the device isolation layer is removed during theformation of the recess region such that a bottom surface of the secondspacer is exposed.
 7. The method of claim 6, wherein the gate electrodeis formed on the device isolation layer.
 8. The method of claim 1,wherein the protective spacer is formed after the compressive stresspattern is formed.
 9. The method of claim 1, further comprising: forminga capping pattern on the gate electrode before forming the first spacer;and removing the capping pattern after forming the compressive stresspattern, wherein the capping pattern is formed of the same material asthe first and third spacers; and wherein the third spacer is preventedfrom being etched by the protective spacer when the capping pattern isremoved. 10-15. (canceled)
 16. A method of forming a semiconductordevice comprising: forming a gate electrode, wherein the gate electrodeincludes at least one sidewall; sequentially forming a first spacer,then a second spacer, and then a third spacer on the sidewall of thegate electrode, wherein each spacer includes at least one sidewall;etching the substrate to form a recess region, wherein the lower portionof the second spacer is removed during the formation of the recessregion such that a gap region is formed between the first spacer and thethird spacer; performing a selective epitaxial growth process in therecess to form a compressive stress pattern in the recess region; andforming a protective spacer on the sidewall of the third spacer andfilling the gap region with the protective spacer.
 17. The method ofclaim 16, further comprising doping the compressive stress pattern withp-type dopant.
 18. The method of claim 16, wherein the compressivestress patterns comprise crystalline silicon-germanium.
 19. The methodof claim 16, wherein the etching of the substrate to form the recessregion comprises: selectively etching portions of the substrate to formpreliminary recess regions on opposite sides of the gate electrode,wherein inner surfaces of the preliminary recess regions react withoxygen to form a first natural oxide layer; removing the first naturaloxide layer via etching; then further etching the preliminary recessregions to form the recess regions, wherein inner surfaces of the recessregions react with oxygen to form a second natural oxide layer; removingthe second natural oxide layer via etching, wherein a lower portion ofthe second spacer proximate the substrate is removed when the secondnatural oxide layer is removed.
 20. The method of claim 16, furthercomprising: covering a top surface of the gate electrode, remote fromthe substrate, with a lower capping pattern comprising a silicon oxide;and covering the lower capping pattern with an upper capping patterncomprising silicon nitride.